Development of a hemispherical silicon image sensor based on shape transformable multi-block plastic-elastomer framework

Abstract

As the demand for three-dimensional electronic devices increases, integration of high- performance inorganic electronics onto three-dimensional （3D） non-planar geometries is a fundamental challenge in the development of next-generation conformable systems. Conventional semiconductor manufacturing methods are confined to planar substrates, which do not geometrically match the curved surfaces required by optical, biological, and structural applications. This thesis presents a residual stress-driven shape transformable framework based on multi-block thermoplastic-elastomer frameworks that bridges this gap. The platform is validated across device integration studies, establishing both the mechanical reliability and the functional performance of integrated inorganic electronics through the full deformation process. Chapter 1 provides a comprehensive review of existing strategies for flexible and 3D electronics, categorized by their primary deformation mechanism. In particular, this chapter provides an overview of the mechanical properties of electronic materials, the thermal properties of thermoplastic plastics, and shape-deforming electronic devices in systems combining these. Chapter 2 addresses the experimental and computational investigation of functional inorganic device integration on the acrylonitrile-butadiene-styrene （ABS）-Ecoflex shape transformable framework. A membrane-type electrode and an indium-gallium-zinc-oxide （IGZO） thin-film transistor array are mounted onto the framework and thermally actuated into cylindrical geometries. The electrical characteristics of the electronic device are measured after transformation, and the validity of the plastic-elastomer framework at the electronic device level is additionally verified through FEM simulation. Chapter 3 extends the framework to the polycarbonate （PC）-ABS-Ecoflex framework capable of sequential, two-step 3D transformation, and applies it to the fabrication of a hemispherical silicon image sensor array. By combining systematically optimized shrinkage of outer ABS rim and an inner Archimedes spiral PC element, a stable hemispherical geometry with a height-to-radius ratio of 74% is achieved. The integrated 91-pixel single- crystal silicon photodiode array demonstrates a pixel yield of 98.9%, detects off-axis laser irradiation at polar angles up to ±82°, establishing the practical feasibility of the residual stress-driven framework for high-performance 3D optoelectronic systems with an extended field of view.